A pressing need exists for low-cost, quantitative, point-of-care diagnostic tools in situations where laboratory resources and trained personnel are not readily available. Enzyme Linked Immunosorbent Assays (ELISAs) are currently the gold standard for diagnosing acute febrile illnesses such as dengue. A high level of system integration is necessary for replicating the functionality of a diagnostic assay protocol in an inexpensive, hand-held easy-to-use device. The use of magnetic beads as labels is particularly attractive in this context since magnetic beads can be both electromagnetically manipulated and detected in opaque solutions and the background biological magnetic noise is insignificant. To leverage these advantages, we are developing a magnetic bead based assay platform with a functionalized Complementary Metal-Oxide-Semiconductor (CMOS) Integrated Circuit (1C) acting as the assay substrate. We propose to implement a magnetic bead label based assay platform using CMOS, a technology chosen for its low cost, design flexibility and manufacturability. A single CMOS chip combines the magnetic bead separation, the magnetic bead detection and the necessary analog and digital signal processing circuitry. The sensor will consist of a low-cost CMOS chip, while the sample preparation relies on an inexpensive membrane filter. This design obviates the need for micro-fluidics and the associated complexity and cost. The sensor device we propose will be low-cost, robust and easy-to-use for rapid point-of-care diagnostics. While the initial applications pertain to dengue immunoassays, the flexibility of this assay platform enables considerable versatility. This integration of magnetic bead detection and sample preparation will provide an inexpensive and versatile platform that could be used with various diagnostic assays by functionalizing the chip surface with different antigen/antibody combinations or incorporating detection of nucleic acid.